1. Field of the Invention
The present invention relates to a volume resistivity measurement apparatus for a dielectric layer of an electrostatic chuck, and to a method using the apparatus.
2. Description of the Related Art
An electrostatic chuck is used for sucking and holding a semiconductor substrate, for example, in the case of performing a variety of treatments such as deposition and etching for the semiconductor substrate or in the case of carrying the semiconductor substrate among treatment apparatuses in a manufacturing process of a semiconductor device. As such an electrostatic chuck, there is one including a plate-like base made of ceramics, in which one of planes of the base is a holding surface of the semiconductor substrate, and an electrostatic electrode is embedded in the base in the vicinity of the holding surface. When electric power is supplied to the electrostatic electrode from the outside, a region between the electrostatic electrode and the holding surface in the base is polarized to become a dielectric layer. Then, electrostatic force is generated on the holding surface, thus making it possible to suck the semiconductor substrate. In the electrostatic chuck having such a basic principle, main suction force for holding the substrate is broadly divided based on volume resistivity of the dielectric layer. In this connection, there are an electrostatic chuck using Coulomb force as main suction force, and an electrostatic chuck using Johnson-Rahbek force as main suction force.
The volume resistivity of the dielectric layer of the electrostatic chuck is an important factor that affects product characteristics of the electrostatic chuck, and the dielectric layer is required to have predetermined volume resistivity. This volume resistivity of the dielectric layer of the electrostatic chuck is sometimes varied depending on manufacturing conditions thereof in a manufacturing process of the electrostatic chuck. Therefore, it is useful to confirm the volume resistivity of the dielectric layer of the manufactured electrostatic chuck in order also to enhance yield of the product.
Heretofore, as a method of measuring the volume resistivity of the electrostatic chuck having the base made of ceramics, there has been a method conforming to JIS-K6911. Moreover, in the case of carrying out the above-described method conforming to JIS-K6911, thermal sticking sometimes occurs on conductive rubbers coated on surfaces of electrodes, which are in contact with a sample. In order to prevent the thermal sticking, there has been a volume resistivity measurement apparatus in which a current limiting resistor is connected in series to a direct-current power supply (Japanese Patent. Laid-Open Publication No. 2000-88900).
However, these method and apparatus are ones to arrange opposite electrodes so that the opposite electrodes can sandwich such a measurement sample therebetween, and then to measure the volume resistivity between the opposite electrodes. Accordingly, when the measurement sample is the electrostatic chuck, these method and apparatus are ones to entirely measure the volume resistivity of the base of the electrostatic chuck. Therefore, these method and apparatus are not ones to partially measure the volume resistivity of the dielectric layer of the electrostatic chuck.
Therefore, heretofore, in order to measure the volume resistivity of only the dielectric layer of the electrostatic chuck, the following procedures have been taken. First, a hole that reaches the electrostatic electrode embedded in the base is drilled from a surface of the base, which is opposite with the holding surface. Then, a part of the electrostatic electrode is exposed to a bottom surface of the hole, a measurement terminal is electrically connected to the exposed electrostatic electrode, and the electrostatic electrode is utilized as one of measuring electrodes. In addition, the other measuring electrode is provided on a surface of the dielectric layer, that is, on the holding surface of the base in a manner of being opposite to the above-described one measuring electrode. Then, a voltage is applied between these measuring electrodes, and a current value is measured. In such a way, the volume resistivity has been obtained.
In the method as described above, which is of measuring the volume resistivity of the dielectric layer by drilling the hole that reaches the electrostatic electrode embedded in the base from the opposite surface of the base with the holding surface, and by exposing a part of the electrostatic electrode to the bottom surface of the hole, time and labor are required for a drilling process of the hole when the base of the electrostatic chuck is made of ceramics. The measurement of the volume resistivity of the dielectric layer is performed in order to confirm whether or not the electrostatic chucks have the predetermined volume resistivity for each of lots among which the manufacturing conditions sometimes differ. Hence, in the case where the time and the labor are required for the drilling process implemented in order to measure the volume resistivity, when an electrostatic chuck defective in terms of the volume resistivity occurs, it takes time to give feedback to discontinue production of the electrostatic chucks. This may undesirably result in manufacture of a large quantity of defective pieces.
The present invention advantageously solves the above-described problems. It is an object of the present invention to provide a volume resistivity measurement apparatus for a dielectric layer of an electrostatic chuck, which makes it possible to measure the volume resistivity of the dielectric layer of the electrostatic chuck without implementing the drilling process for the electrostatic chuck to be manufactured, thus enabling rapid measurement of the volume resistivity, and to provide a measurement method using the apparatus.